False-colour X-ray of a seahorse, Hippocampus sp., in side view. The external bony skeleton of this seahorse consists of rings around the head, trunk and tail, and some of these bony plates have spines. Part of the gut (blue) can be seen in the abdomen. The gill cavity is behind each eye. Seahorses move slowly using fins (not seen here); their tail can be used to anchor the animal to seaweed or coral. It is the male seahorse that incubates the fertilized eggs in a brood pouch on his abdomen. There are many species of Hippocampus distributed from the Mediterranean to the North Sea, and in tropical waters. Magnification: x0.5 at 35mm size.